First it’s good for you, now it’s bad. What is the truth about HRT?

Complicated. It is true that hormone replacement therapy is no longer regarded as an “elixir of life”, as an HRT proponent once described it. More evidence was published this week that will discourage some women from taking it, but most doctors believe that HRT still has a part to play.

How did it all start?

HRT emerged in the 1950s as medicine addressed the menopause. Women had always endured symptoms such as hot flushes and night sweats at the change of life, but the emergence of hormone pills seemed to offer a cure.

The popularity of HRT was boosted by books such as Feminine Forever, published in 1966 by the American physician Robert Wilson. Premarin, a pill containing the female sex hormone oestrogen, became one of the bestselling drugs in the US. Progress was slower in Britain but here, too, HRT had its champions – including Wendy Cooper, the journalist and author, and Teresa Gorman, the MP. Ms Cooper’s book No Change ran through nine editions.

Did it work?

For some women HRT undoubtedly alleviates menopausal symptoms. Studies also began to appear suggesting that HRT brought a lot of other benefits, including a lower risk of heart attack.

Users of the combined pill (oestrogen plus progesterone) also showed lower risks for endometrial cancer. By the mid1990s researchers had claimed that HRT could reduce the risks of Alzheimer’s, age-related macular degeneration, colon cancer, tooth loss, diabetes, Parkinson’s disease and osteoporosis.

That sounds good, doesn’t it?

A bit too good, maybe. Heart disease is a leading cause of death among older women, claiming nine times more lives than breast cancer. So if HRT really was protective, it could have had huge health benefits. Doctors were convinced that women on HRT lived longer, healthier lives.

However, the women they were studying were not typical: they were already healthier, so would have lived longer anyway.

What changed people’s minds?

In the 1990s two large-scale trials, funded by the US Government and Cancer Research UK, were launched to test the veracity of these claims. The suspicion was that the earlier trials had been on too small a scale and were methodologically unsound, so their conclusions could not be trusted.

What were the new studies?

The two main ones were the Women’s Health Initiative (WHI) trial in the US, and the Million Women Study in Britain. Both were large, well-planned studies and from 2002 they began to produce results that shook confidence in HRT.

What did they show?

The WHI was the first to publish. It was due to report in 2005 but was terminated in 2002 because of evidence that the combined oestrogen-progesterone pill increased the risk of breast cancer. The following year it reported that far from reducing the risk of heart disease, the combined pill increased it. The Million Women Study also produced disquieting findings. Women using the combined pill were twice as likely to develop breast cancer, and other forms of HRT also increased the risk, though not by as much. In simple terms it showed that while among 1,000 postmenopausal women aged between 50 and 60 there would be 20 breast cancer cases normally, among users of the combined pill there would be an extra 19 cases.

What about other diseases?

The verdict is mixed. The Million Women Study showed a 20 per cent increase in risk of dying of ovarian cancer – one extra case for every 2,500 women taking HRT over five years – while the WHI found HRT gave no protection against Alzheimer’s disease. Indeed, there was a doubling of the risk in women over 65. The only bright spot was a reduced risk of hip fractures and colorectal cancer found by the WHI trial, but the benefits of these are not great enough to justify taking HRT.

That sounds pretty damning, doesn’t it?

Yes, and millions of women around the world stopped taking HRT as a result of the findings. In Britain it was estimated that users halved from two million to a million in under a year.

But haven’t I read claims that the conclusions of the WHI trial on heart disease have since been disproved?

Yes, that has been claimed. A fresh analysis of the study showed that the heart disease rise was concentrated in older women. Among those 50 to 59, the use of HRT reduced the damage to coronary arteries, suggesting that in this age group it is protective rather than damaging. The reason, it is believed, is that the blood vessels of younger women are different from those of older ones.

Do these effects last after a woman stops taking HRT?

This is an important question because many women with severe menopausal symptoms are still being given HRT for short periods, typically a few years.

The latest research, a follow-up to the WHI, was published this week. It showed that the increased heart risks found in the original study – where the average age of the women was 63 – disappeared in the three years after women stopping taking it, as did the benefits of reduced bone fractures and colorectal cancer. But the increased risks of breast cancer continued. This was a surprise to the investigators, who had expected the risks to revert to normal as soon as the women stopped taking HRT. In fact, women who had taken the combined pill then stopped were 27 per cent more likely to develop breast cancer in the next three years than women who had never taken it.

The study also worked out a “global index” of risks and benefits, which included heart disease, breast cancer, stroke, blood clots in the lung, endometrial and colorectal cancer, hip fractures and deaths owing to other causes. This global index was 12 per cent higher in women who had taken the combined pill for an average of 5½ years, and did not diminish much after they stopped taking it.

So where does all this leave us?

HRT does have benefits in alleviating menopausal symptoms, and it is important not to overlook those when enumerating the risks. For women who suffer badly, the benefits of a short course of HRT still exceed the risks, so long as the dose is the minimum to achieve an effect, and the treatment is as short as possible.

But they do suggest that HRT should not be used in women who have an easy menopause, or prolonged indefinitely in the hope of preserving youth. That this was ever done was a triumph of marketing over science, as one HRT critic put it.

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